Ignition and automatic pilot control



Feb. 22, 1955 c. K. STROBEL 2,702,593

IGNITION AND AUTOMATIC PILOT CONTROL FOR FUEL BURNERS Filed Dec. 18, 1950 g: r Q QB uE g g F 6 & V

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BY Q M United States Patent IGNITION AND AUTOMATIC PILOT CONTROL FOR FUEL BURNERS Charles K. Strobel, Pittsburgh, Pa., assignor to Robertshaw-Fulton Controls Company, Greensburg, Pa., a corporation of Delaware Application December 18, 1950, Serial No. 201,410

5 Claims. (Cl. 158-128) This invention relates to ignition and automatic pilot controls for fuel burners and more particularly to electric ignition systems wherein the automatic pilot control serves to shut off the flow of fuel to both the main and pilot burners upon extinguishment of the flame.

An object of the invention is to simplify existing arrangements for obtaining the so-called 100% shut off of fuel to the burners.

Another object of the invention is to utilize the source of electric energy for the igniter to operate a simple timing device during the starting operation.

Another object of the invention is to control the starting operation manually while providing an automatic shut off in the event of extinguishment of the flame.

Another object of the invention is to obviate the necessity of manually holding a starting button for an extended eriod.

p In a preferred embodiment of the invention, a control means is biased to a fuel flow preventing position and is adapted for controlling the fuel supply to an ignition pilot burner which serves to ignite the main burner. An electric catalytic igniter is employed for igniting the ignition burner upon emission of fuel therefrom. A manually operable means serves to move the control means to a fuel flow permitting position after which it becomes latched for a predetermined period set by a timing device. The timing device comprises a bimetal element heated by an electric heater which is controlled by a switch associated with the latch.

A stand-by pilot burner is lighted by the ignition burner and serves to maintain the thermal element of the automatic pilot control in condition for supply of fuel to the main burner. Consequently, under normal running conditions the ignition burner is shut off by operation of the timing device on the control means, but the stand-by pilot continues to produce flame for heating the thermal element and maintaining the main burner in operation. Upon extinguishment of the stand-by pilot the automatic pilot control comes into operation to shut off all fuel to the burners.

Objects and advantages additional to those hereinabove set forth will become apparent from the following description, taken in connection with the accompanying drawing, which shows the preferred embodiment by way of example in a schematic view of the complete system.

Referring more particularly to the drawing, the automatic pilot control and ignition apparatus is shown in conjunction with a main burner -which is supplied with fuel by a main fuel pipe 12. A stand-by pilot burner 14 is positioned in lighting proximity to the main burner 10 and is supplied with fuel from the main fuel pipe 12 by way of a conduit 16.

The flow of fuel to the main burner 10 and the standby pilot burner 14 is under control of an automatic pilot valve 18 positioned in the main fuel pipe 12. The automatic pilot valve 18 may be of any known form and in this embodiment is shown as comprising a capillary tube 20 and bulb 22 containing a thermally responsive fluid, such as mercury. The bulb 22 is exposed to a flame from the stand-by pilot burner 14 and, as is customary in such devices, the valve 18 will be maintained in an open position for flow of fuel in the main fuel pipe 12 as long as the bulb 22 is sufficiently heated. However, upon extinguishment of the flame at the stand-by pilot burner 14, then the bulb 22 will become cool and the valve 18 will close to shut off the supply of fuel to both the standby pilot burner 14 and the main burner 10.

2,702,593 Patented Feb. 22, 1955 The flow of fuel in the main fuel pipe 12 to the automatic pilot valve 18 is under control of a manually operable control means, such as a gas cock 24. It will be understood that the gas cock 24 may be a component part of an oven thermostat (not shown) responsive to the heat of the main burner 10 but, as such combinations are well known to those skilled in the art, further description is deemed unnecessary except to point out that the flow of fuel in the main fuel pipe 12 and conduit 16 is throttled by operation of the thermostat.

The control means of this invention take the form of a valve casing 26 having an inlet 28 connected by a conduit 30 to the outlet of the gas cock 24. In the event that a combined thermostat and gas cock 24 is utilized, then the conduit 30 could form the pilot connection on the thermostat so that unthrottled gas would be supplied to the inlet 28. In either event, the gas cock 24 will open and close communication between the main fuel pipe 12 and the conduit 30 whenever the flow of fuel in the main fuel pipe 12 is likewise controlled.

An outlet 31 is provided in the casing 26 for connection with an ignition pilot burner 32. The ignition pilot burner 32 is located in lighting proximity to the stand-by pilot burner 14 for a purpose apparent hereinafter. For starting purposes, the ignition burner 32 also is positioned for heating the bulb 22 of the automatic valve 18 sufliciently to open the same. The flow of fuel between the inlet 28 and the outlet 31 is under control of control means in the form of a valve member 34 cooperable with a valve seat 36 formed on a hollow partition 38 in the valve casing 26. A coil spring 40 is operative between the casing 26 and the valve member 34 for biasing the latter toward the valve seat 36.

An operating stem 42 projects from the valve member 34 through the partition 38 and exteriorly of the casing 26 for manual operation by means of a push button 44 secured thereto. It will be understood that suitable packing 46 is employed between the valve stem 42 and the casing 26 to prevent leakage of fuel thereby. A stop collar 48 is carried on the valve stem 42 to limit the movement thereof away from the casing 26.

A latching lever 50 is pivoted on the casing 26 and is operatively engageable intermediate its ends by the push button 44. The latching lever 50 has its free end movable into latching engagement with a bimetal element 52 forming part of the timing means of this invention. The bimetal element 52 is pivotally mounted at the opposite end on the casing 26 and is biased by a tension spring 54 toward latching engagement. Such movement is limited by a stop pin 56 which projects from the casing 26 into operative engagement with the bimetal element 52.

An electric catalytic igniter 58 is provided for igniting the ignition pilot burner 32. The catalytic igniter is of the so-called hot type and is consequently energized at all times from a suitable source of current supply indicated by the line wires L1, L2. The usual step-down transformer 60 is provided in the circuit of the igniter 58.

As previously indicated, the source of electric energy L1, L2 for the igniter 58 is utilized to operate the timing device during the starting operation. To this end, an electric heating coil 62 is provided for the bimetal element 52 and is connected in parallel circuit with the igniter 58 by way of wires 64, 66. A control switch comprising a fixed contact 68 and relatively movable contact 70 is carried by the valve casing 26 and serves to control the current supply to the heater coil 62. The control switch 68 is normally biased to open position but is operable to closed position by means of a pin 72 carried on the latching lever 50 for this purpose.

Operation In the operation of the device, the parts are moved to the positions shown in the drawing during the starting operation. Thus, in such operation the main gas cock 24 is rotated to open position to supply fuel to the inlet 28 of the control valve casing 26. The push button 44 is then manually operated to move the valve member 34 away from the valve seat 36 and establish communication between the inlet 28 and the outlet 31. Since the catalytic igniter 58 is assumed to be continuously energized then the fuel flowing from the ignition pilot burner 32 will become ignited. The resulting flame serves to heat the bulb 22 of the automatic pilot valve 18 sufliciently to cause this valve to open and supply fuel to the stand-by pilot burner 14 and the main burner 10. The fuel flowing from the stand-by pilot burner 14 is ignited by the flame from the ignition pilot burner 32 and in turn ignites the fuel flowing from the main burner and supply heat to the bulb 22.

During this starting operation, the latching lever 50 was initially moved by operation of the push button 44 into latching engagement with the bimetal element 52. This operation also served to close the contacts 68, 70 and energize the heater coil 62. The timing device is thus set in operation and, after a predetermined period, the bimetal element 52 becomes Warped for releasing the latching lever 50 and the operating stem 42. Consequently, the valve member 34 is caused to move into engagement with the valve seat 36 under bias of the coil spring 40. Simultaneously with such operation, the contacts 68 and 70 become opened thus deenergizing the heater coil 62. Due to closing of the valve member 34 the flow of fuel to the ignition pilot burner 32 is shut off and the system is placed in steady state or normal running operation.

Upon extinguishment of the flame at the stand-by pilot burner 14 the bulb element 22 will become cooled and the valve 18 will close to shut off flow of fuel to both the stand-by pilot burner 14 and the main burner 10. Otherwise the system will remain in steady running condition under control of the oven thermostat which may be associated with the gas cock 24 as previously described.

It will be understood that the illustrated form of the preferred embodiment is schematic only and many modifications will occur to those skilled in the art without departing from the scope of the invention as defined in the appended claims.

I claim:

1. An ignition and automatic pilot control for fluid fuel burners having a main burner, an ignition pilot burner and a stand-by pilot burner, comprising control means biased to a fuel flow preventing position and adapted for controlling the fuel supply to said ignition burner, manually operable means for overcoming said bias and moving said control means to a fuel flow permitting position, ignition means for producing a flame at said ignition burner for igniting said main and said stand-by pilot burners, a latching element operable by said manually operable means for holding said control means in said flow permitting position, a bimetal element cooperable with said latching element and biased toward latching position, electric heating means for said bimetal element, a control switch for said heating means operably associated with said latching element for operation to closed position when said control means is moved to said fuel flow permitting position, said heating means being eifective for causing movement of said bimetal element against said bias and releasing said latching element for movement of said control means toward said fuel flow preventing position after a predetermined period following initiation of said holding operation, and means responsive to a flame at said stand-by pilot burner for controlling the fuel supply to both said main and stand-by pilot burners.

2. An ignition and automatic pilot control as-claimed in claim 1 wherein said ignition means comprises an electrically energized catalytic igniter, and circuit means for energizing said igniter and said heating means from a common source of electric energy.

3. An ignition and automatic pilot control as claimed in claim 2 wherein said catalytic igniter is connected in parallel circuit with said heating means and said control switc 4. An ignition and automatic pilot control for fluid fuel burners having a main burner, an ignition pilot burner and a standby pilot burner, comprising control means biased to a fuel flow preventing position and adapted for controlling the fuel supply to said ignition burner, operating means for moving said control means against said bias to a predetermined fuel flow permitting position, latching means for holding said control means in said predetermined fuel flow permitting position, said latching means including a latching element movable With said control means, timing means cooperable with said latching means for releasing said control means for movement to said biased position, said timing means including a bimetal latching element operatively engageable with the first said latching element when said control means moves to said fuel flow permitting position to hold said control means in said last named position, means operatively connected to said control means and responsive to movement thereof to said fuel flow permitting position for initiating operation of said timing means, ignition means for producing a flame at said ignition burner for igniting said main and said standby pilot burners, and means responsive to a flame at said standby pilot burner for controlling the fuel supply to both said main and standby pilot burners.

5. An ignition and automatic pilot control as claimed in claim 4 wherein said timing means includes electric heating means for said bimetal element and a control switch for said heating means operatively associated with said latching means for operation to closed position when said control means is moved to said fuel flow permitting position.

References Cited in the file of this patent UNITED STATES PATENTS 2,125,473 Vaughan Aug. 2, 1938 2,271,903 Stuckenholt Feb. 3, 1942 2,483,191 Gauger Sept. 27, 1949 2,527,286 Witzel Oct. 24, 1950 2,564,863 Strobel Aug. 21, 1951 2,604,153 Strobel July 22, 1952 2,610,679 Weber Sept. 16, 1952 2,610,680 Witzel Sept. 16, 1952 

